EP3682111A1

EP3682111A1 - Pump arrangement for a hydraulic unit having a pump piston

Info

Publication number: EP3682111A1
Application number: EP18752429.3A
Authority: EP
Inventors: Oliver Gaertner
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2017-09-12
Filing date: 2018-07-30
Publication date: 2020-07-22
Also published as: JP2020532457A; KR20200054195A; DE102017216002A1; KR102646443B1; CN111094743A; US20200180584A1; US10946851B2; JP6987221B2; CN111094743B; WO2019052735A1

Abstract

In a pump arrangement (66) for a hydraulic unit (14) of a vehicle brake system having a pump housing (16) and a pump piston (22) which is guided so as to be displaceable axially back and forth in the pump housing (16), a damping element (68) is provided radially between the pump piston (22) and the pump housing (16), by means of which damping element vibrations of the pump piston (22) which occur during an operation of the pump arrangement (66) are damped.

Description

description

title

Pump arrangement for a hydraulic unit with a pump piston prior art

The invention relates to a pump arrangement for a hydraulic unit of a vehicle brake system with a pump housing and a pump piston in the pump housing axially reciprocally guided pump piston.

Pump pistons are used in a pump assembly of a hydraulic unit to suck hydraulic fluid into an associated pump housing and pump from there under pressure in a hydraulic circuit. This can be provided in hydraulic units of vehicle brake systems, such as in particular ABS / ESP hydraulic units, a regulated brake pressure in brake circuits. For this purpose, usually a radial piston pump is provided, in which a plurality of pump elements each having a pump arrangement extend radially and perpendicular to an axis of an associated drive shaft or shaft.

In this case, the individual pump piston is supported on the shaft of a drive motor to a arranged around the shaft eccentric bearing of an eccentric. Supported in this way, the pump piston is axially displaceable back and forth in the pump housing and an associated pump cylinder by means of the eccentric. In addition, an intake chamber and a pressure chamber or pump interior as well as an inlet valve and an outlet valve are provided in the pump housing. The valves serve to control a hydraulic fluid flow during a pumping movement of the pump piston. Furthermore, a guide ring, a sealing ring and a support ring are arranged within the pump housing low pressure side radially between the pump piston and the pump housing as sealing and guiding elements. The guide ring serves to guide the pump piston in the pump housing, the sealing ring as a fluid seal between the pump interior and a pump outer space and the support ring for supporting the sealing ring. Disclosure of the invention

According to the invention, a pump arrangement is provided for a hydraulic unit of a vehicle brake system with a pump housing and a pump piston guided axially back and forth in the pump housing. It is radially between the pump piston and the pump housing a

Damping provided by means of which occurring during operation of the pump assembly vibrations of the pump piston are damped.

As a rule, vibration occurs during operation of the pump arrangement substantially during a rotational movement of an eccentric bearing on the eccentric bearing itself, which vibrations are transmitted to the pump piston or piston supported there. In particular, this vibration or vibrations of the piston caused radially to its piston axis. The vibrations thus caused are attenuated by means of the damping element according to the invention to the effect that the vibrations of the piston are minimized or even prevented in their frequencies and amplitudes. In this way, vibrations can not be transmitted to sealing and guiding elements that surround the piston. Otherwise, such vibrations destabilize the sealing elements in their sealing and the guide elements in their leading effect. Thus, by means of the damping element according to the invention a sealing and guiding situation during operation of the pump assembly can be significantly improved. An undesirable introduction of air into a hydraulic system and / or a leakage of the brake fluid can be greatly reduced or prevented. It can be provided on the hydraulic unit a particularly reliable braking effect.

In particular, by means of the damping element according to the invention, an undesired transmission of the vibrations to a sealing ring encompassing the piston is avoided. Thus avoided, the sealing effect of the sealing ring is ensured throughout the operation of the pump assembly. The sealing ring is preferably between a pump to be filled with hydraulic fluid. peninnenraum and a pump outer space arranged. Arranged in this way, the sealing ring can then always reliably act fluid-tight between the pump interior and the pump outer space during operation. The pump outer space is in particular an eccentric space in which the eccentric with its eccentric bearing and its shaft is located. At the eccentric bearing is supported perpendicular to the shaft of the piston, which is to be moved translationally by means of rotational movements of the shaft back and forth. In this case, high-frequency vibrations occur on the eccentric bearing, which are also transmitted to the piston. The piston tends to be within an available range

Guide game to move with vibrations in the high frequency range and associated amplitudes or deflections transversely, in particular radially, to its piston axis. By means of the damping element, these movements can be damped or restricted in their frequency and deflection and even be set completely. Thus, the vibrations can be prevented almost at the point of origin. Otherwise, the corresponding frequencies are transmitted in particular to the sealing ring, the material of which can often not follow the high-frequency deflections as a function of its temperature. The piston lifts off from the sealing ring. A gap is created between the piston and the sealing ring, which reduces the fluid-sealing effect of the sealing ring.

Such a gap formation is reliably prevented according to the invention.

Preferably, the damping element according to the invention has a purely vibration-damping function and no fluid-sealing function, as is required in a sealing ring. Thus, a functional material for the damping element can always be selected, with the targeted his vibration-damping properties can be optimized. There is no need to compromise on a fluid-tight effect required in a sealing ring.

Furthermore, according to the invention, a sealing ring is advantageously provided radially between the pump piston and the pump housing for sealing a pressure space to be filled with hydraulic fluid to be filled with the hydraulic fluid, wherein the sealing ring is arranged on the side of the damping element facing the pressure chamber. Arranged in such a way, is with the sealing ring due to its fluid-sealing effect prevents contact of the hydraulic fluid with the damping element. As already described, it is simultaneously ensured by means of the damping element according to the invention that the sealing ring reliably acts sealingly over the entire operation of the pump arrangement. This is always ensured that the damping element with the hydraulic fluid is not in

Contact comes and the hydraulic fluid can not damage the material acting on the damping element. Thus, the damping element has a long life. In addition, the damping element does not have to have a hydraulic fluid-resistant material. The material can be cost-effective and functionally designed purely for its damping function.

Advantageously according to the invention the damping element is made of a material which has a different degree of hardness than the material from which the sealing ring is designed. Preferably, the material of the damping element has a higher degree of hardness than the material of the sealing ring. A greater degree of hardness has the material of the damping element in particular if it has a greater hardness and / or strength than the material of the sealing ring. By hardness is meant a mechanical resistance which the material opposes to a mechanical penetration of another body. The term "strength" refers to a resistance that the material has to deformation or separation. So designed, the material of the damping element has a greater resistance to deformation by means of the vibrations of the piston. Thus, the material of the damping element can specifically counteract the vibrations of the piston during operation and dampen the vibrations while the material of the sealing ring is not loaded. The material of the sealing ring acts reliably sealing during the entire operation.

Alternatively, the damping element is advantageously made of a material that has a lower degree of hardness than the material of the sealing ring. Such

Design can be advantageous under certain conditions. The materials of the damping element and the sealing ring preferably do not differ primarily in the degree of hardness in order to fulfill their function, but in their material itself, in particular in their elastic and / or viscoelastic properties. Particularly preferably, the material of the damping element has greater elastic and / or viscoelastic properties than the material of the sealing ring. An elasticity causes the damping element can deform immediately and reversibly. Viscoelastic properties are partially elastic and partly viscous. Due to the elastic properties, the damping element deforms immediately, limited and reversible, while it deforms time-dependent, unlimited and irreversible due to the viscous properties. Thus, the vibrations of the piston can not only be absorbed by the elastic properties of the material of the damping element and released again, but are absorbed by the viscous properties in the material itself. It is achieved a particularly good damping effect of the damping element on the vibrations of the piston, especially in the high frequency range. In a deformation of the material of the damping element with the greater elastic and / or viscoelastic properties in comparison to the material of the sealing ring act correspondingly larger elastic counter forces of the damping element on the piston. The material of the sealing ring is in this respect not affected by the vibrations of the piston.

If the material of the sealing ring preferably has a greater degree of hardness than the material of the damping element, the sealing ring can deform less than the damping element. The sealing ring is reliably sealingly attached to the piston, while the vibrations of the piston are absorbed by the damping element by means of its higher elasticity or viscoelasticity.

Furthermore, the damping element according to the invention is advantageously designed with an elastomer. An elastomer is a dimensionally stable, elastically deformable polymer. The elastomer can change its shape by pressure for a short time and quickly return to its original shape after the end of the pressure. The elastomer is widely meshed and therefore flexible. So flexible, the elastomer can absorb the vibrations of the piston particularly quickly and extensively vibration damping. The elastomers include all types of crosslinked rubber. Preferred elastomers are natural rubber (NR), acrylonitrile-butadiene rubber (NBR), styrene-butadiene rubber (SBR), chloroprene rubber (CR), butadiene rubber (BR) and ethylene-propylene-diene rubber. Rubber (EPDM). Preferably, the elastomer is designed with EPDM. EPDM has a particularly high elasticity, with which the vibrations can be absorbed absorbing and with which the damping element can then return to its original shape.

Preferably, the damping element is designed with an elastomer that is not hydraulic fluid resistant, in particular not resistant to brake fluid. Such a damping element is inexpensive and can be targeted to its vibration-damping function.

Furthermore, the damping element according to the invention advantageously with a

Viscoelastomer designed and thus has viscoelastic properties. With the viscoelastic properties, as already described, the vibrations of the piston can be attenuated particularly comprehensively.

In addition, according to the invention, the damping element preferably has a piston contact surface for application to a piston outer surface of the piston and a support surface facing away from the piston contact surface for support against an inner surface in the pump housing or housing. The piston contact surface is smaller than the support surface. With such a smaller piston contact surface has the

Damping element piston side a smaller surface than the housing side. In and on the housing, the damping element with such a larger support surface can rest stable and vibration damping over a wide range. At the same time, a friction between the piston outer surface and the piston contact surface of the damping element can be kept as low as possible when the piston is moved back and forth. It can move the piston largely unimpeded translational and the damping element wears due to friction only slightly. Structurally particularly simple, the inner surface is preferably directly the inner surface of the housing as a housing inner surface.

In addition, the damping element according to the invention advantageously has a piston contact surface for application to a piston outer surface of the piston, wherein the piston contact surface is designed with a friction-reducing coating. The friction-reducing coating is a coating which has a lower coefficient of friction than the material of the damping elements without friction-reducing coating. By means of such a coating, a friction between the piston outer surface and the piston contact surface when reciprocating the piston is minimized. For this purpose, the friction-reducing coating is preferably a smooth-lacquer coating and / or a grease coating or greasing. The smooth paint coating creates a particularly smooth and low-friction surface. More preferably, the smooth paint coating has a silicone and / or polytetrafluoroethylene (PTFE) base. With the silicone or polysiloxane-based coating is achieved, which is particularly flexible and does not hinder the damping element in its damping effect. With the PTFE base, a coating is created which has a particularly low coefficient of friction and in which a static friction corresponds in size to a sliding friction between two bodies. This can take place when starting a movement of the piston, a transition from a standstill to movement without jerk or stick-slip effect.

Further, the damping element according to the invention advantageously has a piston contact surface for application to a piston outer surface of the piston and a support surface facing away from the piston contact surface for supporting on an inner surface in the housing, the damping element is made with a first and a second material and is the piston contact surface with the first material formed with the second material, the support surface. In this case, the first material to the piston outer surface has a lower coefficient of friction than the second material to the inner surface. In particular, the first material to the piston outer surface has a lower sliding friction than the second material to the inner surface. Thus, the piston is almost not braked during its translational movement on its outer piston surface and the damping element is protected against a friction-related wear. At the same time, the damping element is supported comparatively stably in and on the housing at its support surface by means of the second material, which bears against the inner surface, with the higher coefficient of friction than the first material. The inner surface in the housing is preferably a piston-facing inner surface of a housing arranged in the component, such as a guide ring. Structurally particularly preferred, the inner surface is directly the inner surface of the housing as the housing inner surface. Preferably, the first material is PTFE, which is often referred to by the trade name Teflon from DuPont. PTFE is outstanding low friction and very dimensionally stable. Thus, no significant shear forces between the housing and the piston act. Damage to the damping element by means of compression due to such shear forces can be safely avoided.

Furthermore, with PTFE an undesirable stick-slip effect is prevented.

Advantageously, the second material is an elastomer. With the elastomer, a greater sliding friction of the damping element to the inner surface in the housing is created compared to the first material. Thus, the damping element during the back and forth of the piston is relatively stable positioned on the housing. At the same time, the elastomer has the already described dimensionally stable and elastic properties, which are particularly advantageous for the vibration-damping function of the damping element. The elastomer damps the radial vibrations of the piston particularly reliably, while the piston can slide past the first material of the damping element almost unimpeded. The elastomers used are preferably the elastomers already described, particularly preferably EPDM. Alternatively or additionally, the second material is preferably designed with a viscoelastomer, with which the advantages already described can be achieved.

Preferably, the damping element surrounds the piston only partially. So embraced, a friction between the damping element and the piston can be reduced with sufficiently strong damping.

According to the invention particularly advantageous, the damping element has a ring shape which is circumferentially embracing the pump piston. Designed in this way, the piston is stably gripped by the annular shape of the damping element over its entire circumference, and a particularly uniform damping-reducing effect is achieved.

By means of the ring shape, a circular damping ring is formed whose cross-section is preferably designed in terms of manufacturing technology simply O-shaped or rectangular. Particularly preferably, the annular shape has a rectangular cross section, in which a corner is chamfered or stepped on the piston side. For a smaller piston contact surface is achieved in comparison to the support surface with the advantages already mentioned. Advantageously, the ring shape is designed with a rectangular cross-section, which on the housing side alternatively or additionally has a bevel or stepping off of a corner. Thus, the damping ring can be selectively fitted or supported in the pump housing. Most preferably, the ring shape is designed as a quadring with an approximately square cross-section. Between the corners of the square in each case a recess in the material is provided. Such a quadring is less rigid in the radial direction compared to the O-ring or rectangular ring and can be better deformed when absorbing vibrations of the piston. In addition, thanks to its indentation, the Quadring has a lower piston contact surface than a rectangular ring to reduce friction. Further, the recess for receiving a lubricant for a lower friction serve.

In a design of the damping element with a first and a second material, wherein the first material, the piston contact surface and the second material forms the support surface, and the first material to the piston outer surface having a lower coefficient of friction than the second material to the inner surface, it is preferred that the cross section to make the damping element so that the damping element with its first material has a trapezoidal cross-section, the longer base side is arranged on the piston side. There, the vibrations of the piston can be absorbed over a wide range. Thus, although a larger friction surface of the piston contact surface is reached, but this does not significantly affect the piston thanks to the low-friction first material in its translational movement.

In addition, according to the invention advantageously has the ring shape at least one damping ring section. The annular shape thereby stably surrounds the piston, while the damping effect of the damping element with the at least one damping ring section takes place only in sections. With such a section damping, the friction is reduced to the piston outer surface. For this purpose, at least two damping ring sections of the ring shape are preferably provided, with which the damping effect is distributed uniformly over the ring shape. Particularly preferably, the ring shape is at its inner radius with at least one circular arc-shaped, from the damping ring radially inward divide Henden circle segment provided as a damping ring section. The at least one circular segment forms the piston contact surface on the piston side. Such a segmented circular ring has a smaller piston contact surface compared to the support surface which extends radially outward on the damping ring and is nevertheless stably positioned with the ring shape around the piston.

Furthermore, according to the invention, a guide ring for guiding the piston in the housing is preferably provided radially between the piston and the housing, wherein the damping element is implemented in the guide ring, in particular integrated. Implemented in this way, the damping element together with the guide ring can be particularly easily assembled to measure and in the right place in the housing. For this purpose, the damping element is preferably arranged on the piston side adjacent to the piston and on the housing side adjoining the guide ring and accommodated in an exact location in an annular step of the guide ring. Thus, the damping element is stably positioned in the guide ring and can act directly damping the piston.

Preferably, the damping element is implemented for easy mounting to a mating interface in the housing before further components of the pump element are to be inserted. Particularly preferably, the damping element is manufacturing technology simply mounted on or around the piston and can be installed as an assembly with the piston in the housing.

Exemplary embodiments of the solution according to the invention will be explained in more detail below with reference to the attached schematic drawings. It shows:

1 shows a cross section of a pump assembly of a hydraulic unit according to the prior art,

2 is a highly schematic representation of the view of FIG. 1 during operation,

3 shows the view according to FIG. 2 of a first embodiment of a pump arrangement according to the invention, FIG.

4 shows the view according to FIG. 2 of a second embodiment of a pump arrangement according to the invention, FIG. 5 is a plan view of a first variant of the damping element according to the invention,

6 shows the section Vl-Vl of FIG. 5,

7 is a sectional oblique view of a second variant of the damping element according to the invention,

8 shows the view according to FIG. 8 of a third variant of the damping element according to the invention, FIG.

9 shows the view according to FIG. 8 of a fourth variant of the damping element according to the invention, FIG.

10 shows the section X-X of FIG. 5 of a fifth variant of the damping element according to the invention,

11 is a sectional oblique view of a sixth variant of the damping element according to the invention,

12 is a sectional oblique view of a seventh variant of the damping element according to the invention, and

Fig. 13 is a plan view of an eighth variant of the damping element according to the invention.

In Fig. 1 and 2, a pump element 10 is shown only partially shown radial piston pump 12 within a hydraulic unit 14 of a vehicle brake system only partially shown. The pump element 10 comprises a pump housing or housing 16, which is designed by means of a bore 18 in a hydraulic block 20. Further, the pump element 10 includes a pump piston or piston 22, which is to be moved by means of an eccentric 24 within the housing 16 translationally back and forth or to move. The eccentric 24 includes an eccentric drive not shown drive shaft and an eccentric bearing 26 to which the piston 22 is supported substantially vertically and radially.

The piston 22 is presently a multipart pump piston. To this end, the piston 22 comprises a piston ram 28 supported on the eccentric bearing 26 and a piston sleeve 30 adjoining the piston ram 28 with an inlet 32. Through the inlet 32, a brake fluid can flow radially inwards into the piston sleeve 30 as hydraulic fluid. From the piston sleeve 30, an inlet valve 34 carries the brake fluid into a high-pressure region 36, that of a piston sleeve 30th encompassing cylinder cup 38 is enclosed. Radially between the cylinder cup 38 and the piston sleeve 30, an annular piston sealing element 40 is arranged, with which the high-pressure region 36 is sealed against a low-pressure region 42 belonging to the piston sleeve 30 and the inlet 32.

Thus sealed, the piston 22 is guided along its piston axis 44 back and forth axially displaceable by means of the eccentric 24 in the cylinder cup 38. The cylinder cup 38 forms part of a multi-part pump cylinder 46, to which furthermore an annular filter 48 arranged around the piston sleeve 30 belongs. The filter 48 filters the brake fluid flowing in through the inlet 32.

At the same time, the filter 48 supports a sealing arrangement 50 axially relative to a housing stage 52 of the housing 16. The seal assembly 50 is also sealing radially on the outside of the housing 16 and radially inwardly on the piston 22. In this way, the sealing arrangement 50 separates a pump interior or pressure chamber 54 to be sealed from a pump outer space 56. Ambient pressure prevails in the pump outer space 56, whereas a pump pressure arises in the pressure space 54 during operation of the pump element 10. The pressure chamber 54 is filled with a retraction of the piston 22 from the housing 16 with brake fluid through the inlet 32 therethrough.

The sealing arrangement 50 comprises a guide ring 58, a support ring 60 and a sealing ring 62. The guide ring 58 is located on the side of the sealing arrangement 50 facing the pump outer space 56, is supported radially on the outside of the housing 16 and lies radially inward on a cylindrical piston outer surface 64 of the piston 22 on. Thus, the piston 22 is guided deliberately during its movement and supported transversely to the piston axis 44. Further, the support ring 60 is disposed axially between the guide ring 58 and the sealing ring 62 and serves to support the sealing ring 62. The sealing ring 62 is located on the side facing the pressure chamber 54 of the seal assembly 50 and forms the actual fluid seal between the hydraulic fluid to be filled pressure chamber 54 and the pump outer space 56. The sealing ring 62 is designed for this purpose with a brake fluid-resistant material. Fig. 2 illustrates how 10 vibrations occur on the piston 22 during operation of the pump element. On the piston 22 are transmitted from the eccentric rotating during operation eccentric eccentric 26, the high-frequency vibrations occurring there. In particular, the amplitudes associated with the vibrations extend radially to the piston axis 44, as shown by the double arrow on the piston 22 according to FIG. Starting from the piston 22, the vibrations are transmitted to the sealing ring 62. There, the vibrations cause problems such that the sealing ring 62 with its material can not follow the high-frequency vibrations and the piston 22 lifts from the sealing ring 62. When lifting creates a gap between the sealing ring 62 and the piston 22. The sealing ring 62 can not reliably seal the pressure chamber 54 against the pump outer space 56.

3 to 4 show a pump arrangement 66 according to the invention, in which, in contrast to FIGS. 1 to 2, a radially arranged between the piston 22 and the housing 16 damping element 68 is provided. The damping element 68 is adapted to dampen the frequency and amplitude of the vibrations occurring on the piston 22 during operation of the pump element 10 and thus during operation of the pump arrangement 66.

For this purpose, the damping element 68 is arranged axially between the support ring 60 and the guide ring 58, while the sealing ring 62 is arranged on the pressure chamber 54 facing side of the support ring 60. Thus, the sealing ring 62 is located on the pressure chamber 54 facing side of the damping element 68 and seals the pressure chamber 54 with its located therein brake fluid against the damping element 68 from. The damping element 68 thus does not come into contact with the brake fluid and may be designed with a non-brake fluid-resistant material. The material of the damping element 68 is present ethylene-propylene-diene rubber (EPDM) and has a higher degree of hardness than the material of the sealing ring 62. By means of its vibration damping properties, the damping element 68 prevents a gap formation between the piston outer surface 64 and the housing 16 and the sealing ring 62. Thus, the sealing ring 62 can act reliably sealing over the entire operation of the pump assembly 66 away. In the embodiment of FIG. 3, the damping element 68 has been the piston 22 annularly encompassing mounted as an assembly with the piston 22 in the housing 16 to its matching interface. In the embodiment according to FIG. 4, the damping element 68 is implemented in an annular step 70 directly in the guide ring 58. The damping element 68 and the guide ring 58 form an assembly which is to be installed in the housing 16 such that the damping element 68 faces the pressure chamber 54. Such an assembly is simple and can be targeted. In the assembled state, the damping element 68 has a piston contact surface

72, which bears against the piston outer surface 64 of the piston 22. In addition, the damping element 68 has a support surface 74 which bears against an inner surface 76 in the housing 16 and on which the damping element 68 is supported on the housing 16. According to FIG. 3, the inner surface 76 is a housing inner surface 78 of the housing 16 itself. In the exemplary embodiment according to FIG. 4, the inner surface 76 is a ring inner partial surface 80 of the guide ring 58 that surrounds the damping element 68 in a circumferential manner.

5 to 12 show several variants of a designed with a ring shape 81 damping element 68 which engages around the piston 22 fully. In the variant according to FIG. 6, the damping element 68 is designed as an O-ring with a cross-section which has a circular shape in the unloaded state. In the variants according to FIGS. 7 to 9, a damping element 68 with a rectangular cross-section is provided. FIG. 7 shows a variant in which a rubbing-reducing coating 83 is attached to the piston contact surface 72 on the piston side, which is designed here with polytetrafluoroethylene (PTFE). Such a coating 83 is possible if required in all variants, even if it is not explicitly shown. 8 shows a variant in which by means of a chamfer 84 of a corner 86 of the rectangular shape of the damping element 68 a piston contact surface 72 is formed, which is smaller than the support surface 74 facing away from the piston contact surface 72. For the same purpose, in the variant according to FIG. 9, the corner 86 is graduated by means of a step or groove 88. Fig. 10 shows a variant in which the damping element 68 is designed as a quad ring, while approximately one has a rectangular cross-section with four corners 86. Between each corner 86, a recess 90 is provided, with which the piston abutment surface 72 is reduced compared to a damping element 68 without indentation 90. The damping element 68 according to FIGS. 5 to 10 is produced with EPDM from a single elastomeric material. In the variants according to FIGS. 11 and 12, the damping element 68 has a first material 92 and a second material 94. The second material 94 is designed with EPDM as the elastomer and the first material 92 with PTFE as a particularly low-friction material. With the first material 92, the piston contact surface 72 and with the second material 94 is the

Support surface 74 formed. Thus designed, the first material 92 has a lower coefficient of friction to the piston outer surface 64 than the second material 94 to the inner surface 76 in the housing 16. In addition, the damping element 68 has shown in FIG. 11 designed with the low-friction first material 92 piston contact surface 72, the piston side an additional friction-reducing indentation 90 has. Thus, the piston contact surface 72 in addition to the low-friction material friction-reducing smaller than the support surface 74 designed.

In the variant according to FIG. 12, a material section 96 of the damping element 68 designed with the low-friction material 92 and trapezoidal in cross-section is provided, which forms the piston contact surface 72 with its longer base side. Although the piston contact surface 72 is larger than the support surface 74, a friction loss can be successfully compensated for by means of the low-friction material 92. In addition, the vibrations of the piston 22 can be absorbed into the damping element 68 over a wider area of the larger piston contact surface 72. FIG. 13 shows a variant of the ring shape 81, whose piston contact surface 72 is segmented or extends in sections over the inner circumference 82. For this purpose, a plurality of radially inwardly directed annular segments are provided as damping ring sections 98 on the inner circumference 82, with which the piston abutment surface 72 is formed radially inwardly. In the present case, four such ring sections 98 are preferably distributed uniformly on the inner circumference 82. orderly. In this case, each individual ring section 98 can be designed with a cross section, as already described.

Claims

claims

A pump arrangement (66) for a hydraulic unit (14) of a vehicle brake system having a pump housing (16) and a pump piston (22) guided axially back and forth in the pump housing (16),

characterized in that radially between the pump piston (22) and the pump housing (16) is provided a damping element (68) by means of which during operation of the pump assembly (66) occurring vibrations of the pump piston (22) are damped.

2. Pump arrangement according to claim 1,

characterized in that radially between the pump piston (22) and the pump housing (16) is provided a sealing ring (62) for sealing a in the pump housing (16) arranged to be filled with hydraulic fluid pressure chamber (54), wherein the sealing ring (62) is arranged on the pressure chamber (54) facing side of the damping element (68).

3. Pump arrangement according to claim 2,

characterized in that the damping element (68) is made of a material having a different degree of hardness than the material from which the sealing ring (62) is designed.

4. Pump arrangement according to one of claims 1 to 3,

characterized in that the damping element (68) is designed with an elastomer, which is preferably not hydraulic fluid resistant, more preferably not resistant to brake fluid.

5. Pump arrangement according to one of claims 1 to 4,

characterized in that the damping element (68) has a piston contact surface (72) for application to a piston outer surface (64) of the pump piston (22) and a support surface (74) facing away from the piston contact surface (72). supporting on an inner surface (76, 78, 80) in the pump housing (16), wherein the piston abutment surface (72) is smaller than the support surface (74).

6. Pump arrangement according to one of claims 1 to 5,

characterized in that the damping element (68) has a piston abutment surface (72) for engagement with a piston outer surface (64) of the pump piston (22), the piston abutment surface (72) being formed with a friction reducing coating (83).

7. Pump arrangement according to one of claims 1 to 6,

characterized in that the damping element (68) has a piston abutment surface (72) for engagement with a piston outer surface (64) of the pump piston (22) and a support surface (74) facing away from the piston abutment surface (72) for abutment with an inner surface (76, 78, 80 ) in the pump housing (16), the damping element (68) is made with a first material (92) and a second material (94) and with the first material (92) the piston contact surface (72) and with the second material (94) the support surface (74) is formed, wherein the first material (92) to the piston outer surface (64) has a lower coefficient of friction than the second material (94) to the inner surface (76, 78, 80).

8. Pump arrangement according to one of claims 1 to 7,

characterized in that the damping element (68) has a ring shape (81), which is designed circumferentially encompassing the pump piston (22).

9. Pump arrangement according to claim 8,

characterized in that the annular shape (81) has at least one damping ring portion (98).

10. Pump arrangement according to one of claims 1 to 8,

characterized in that radially between the pump piston (22) and the pump housing (16) a guide ring (58) for guiding the pump piston (22) in the pump housing (16) is provided, wherein the damping element (68) in the guide ring (58). is implemented.